Childhood Sleep Duration and Associated Demographic Characteristics in an English Cohort

Findings

1. Currently available data do not allow the identification of what constitutes “normal” sleep duration for children at different ages. We have shown, in an unselected birth cohort, striking interindividual and intraindividual variation that may result in mislabeling of children with potential sleep disorders when their sleep is within the normal range. Clinicians and parents will benefit from more accurate estimations of normal ranges of sleep duration and sleep awakening in relationship to family characteristics.
2. There are specific demographic characteristics associated with sleep duration during childhood.
3. Total sleep time decreased from an average of 13.2 hours at 6 months to 9.8 hours at 11 years.
4. Nighttime sleep duration did not begin to decline until about 9 years.
5. By school age, most children slept through the night, but about half of children between 18 and 42 months were reported by their parents to wake at least once. Ten percent of infants woke more than three times per night, which decreased over time.
6. Average daytime sleep time at 6 months was 2.4 hours. This number was about 1.2 hours for those children who still took daytime naps, and only 2% of children took naps by age 5.
7. Girls consistently slept five to ten minutes longer than boys.
8. Low birthweight and pre-term infants slept longer.
9. Sleep duration was longer for infants of younger mothers and shorter for those of older mothers.
10. Children from lower SES families tended to go to bed later and rise later.
11. Older children from mothers with lower education tended to sleep slightly longer.
12. Children of non-White ethnicity slept less than White children, and their bedtimes were later.
13. Children in families with many other children slept less.

Limitations

• A limitation of most longitudinal studies conducted over several years is that missing data and loss to follow-up are more likely to occur in the most socioeconomically deprived groups. This study is no different, but its large size means that, even with different rates of loss to follow-up, there is sufficient power to investigate effects in small groups. The number of children in the study fell from 11,478 at 6 months to 7,043 at age 11. The children lost to follow-up over time were mostly from lower socioeconomic status (SES) families with more vulnerable infants.
• Sleep duration at all time points was only available for 4,528 participants.
• Parent reporting of children’s sleep tends to overestimate sleep duration.